Plasma processing apparatus including etching processing apparatus and ashing processing apparatus and plasma processing method using plasma processing apparatus

ABSTRACT

A diameter of a mounting unit of the stage of an asking processing apparatus is less than a diameter of a mounting unit of the stage of an etching processing apparatus, and the diameter of the mounting unit of the stage of the etching processing apparatus is less than a diameter of an objective item.

BACKGROUND OF THE INVENTION

The present invention relates to a plasma processing apparatus, and inparticular, to a plasma processing apparatus capable of reducingdeposited substance fixed onto an objective item to be processed.

In a production process to produce a semiconductor device such as aDynamic Random Access Memory (DRAM) and a microprocessor, there arewidely employed a plasma etching apparatus and a plasma ashing (resistremoving) apparatus which use weakly ionized plasma. With development ofa technique to produce a semiconductor device in finer structure,thickness of the resist thin film becomes smaller. As a result of thereduction of the thickness, it is required in the etching that theresist consuming rate is lowered (the selective ratio is improved) andresist damage is suppressed. For this purpose, processing gas with alarge deposition property capable of generating a large amount ofdeposited substance is often employed in many cases.

When such processing gas is employed, deposited substance is fixed ontoa periphery of a rear surface of the objective item during the plasmaprocessing. That is, in the etching apparatus, a mounting unit thereofto mount the objective item thereon has a diameter smaller than adiameter of the objective item. Therefore, the periphery of the rearsurface of the objective item is exposed during the etching, and thedeposited substance is fixed onto the exposed periphery of rear surfaceof the objective item.

When the deposited substance on the periphery of rear surface peels offfrom a wafer, for example, during transport thereof, the depositedsubstance contaminates as a foreign particle the semiconductor deviceproduction line, leading to yield reduction. Therefore, removal of thedeposited substance is essential to the production line.

To remove the deposited substance on the periphery of the rear surfaceof the objective item or to prevent deposition of such substance, therehave been known a method to supply reactive gas onto the periphery ofthe rear surface to remove the deposited substance (JP-A-2004-200353)and a method in which a cover is disposed over the periphery of the rearsurface to conduct the etching with the cover to thereby prevent thedeposited substance from fixing onto the periphery (JP-A-2004-200219).

SUMMARY OF THE INVENTION

According to the prior art, to remove the deposited substance from theperiphery of the rear surface of the objective item, it is required thata special protective unit is attached onto the periphery or a specialgas is supplied onto the periphery.

When the special protective unit is arranged onto the periphery, theshape of a region etched in the periphery of the objective item isdeformed depending on cases. When the special gas is supplied onto theperiphery, the etching characteristic is changed depending on cases.Therefore, the inherent object of the technique cannot be achieved.

After the etching processing, it is general to conduct ashing processingto remove resist remaining on the surface of the objective item. In theashing processing, plasma is generated using processing gas including,for example, oxygen, hydrogen, water, or ammonia. Radicals dissociatedin the plasma are radiated onto the objective item to resultantly removethe resist.

Similarly, also the deposited substance fixed onto the periphery of therear surface of the objective item when the etching processing isconducted using a gas resulting in a large amount of deposited substancecan be removed by radiating the plasma employed in the ashing. That is,in the ashing processing, when the plasma used in the ashing or theradicals generated by, for example, dissociation in the plasma is or areradiated onto the periphery of the rear surface, the deposited substancecan be removed as in the case of the resist ashing processing.

It is therefore an object of the present invention, which has beendevised on the basis of the knowledge described above, to provide aplasma processing technique capable of removing the deposited substancefixed onto the objective item.

To achieve the object according to the present invention, there isprovided a configuration adopting constituent units as below.

According to the present invention, there is provided a plasmaprocessing apparatus including an etching processing apparatus includinga gas supply unit for supplying an etching gas to a processing chamber,an exhaust unit for lowering pressure in the processing chamber, amounting stage for mounting and for holding in the processing chamber anobjective item to be processed, a transport unit for mounting theobjective item on the stage and for transporting from the stage theobjective item for which processing is finished, and a plasma generatingunit for generating plasma in the processing chamber, and an ashingprocessing apparatus including a gas supply unit for supplying an ashinggas to a processing chamber, an exhaust unit for lowering pressure inthe processing chamber, a mounting stage for mounting and for holding inthe processing chamber an objective item to be processed, a transportunit for mounting the objective item on the stage and for transportingfrom the stage the objective item for which processing is finished, anda plasma generating unit for generating plasma in the processingchamber. A diameter of a mounting unit of the stage of the ashingprocessing apparatus is less than a diameter of a mounting unit of thestage of the etching processing apparatus. The diameter of the mountingunit of the stage of the etching processing apparatus is less than adiameter of the objective item.

Due to the configuration according to the present invention, it ispossible to provide a plasma processing technique capable of removingthe deposited substance fixed onto the objective item.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram to explain a first embodiment of a plasma processingapparatus of the present invention.

FIG. 2 is a diagram to explain details of a region in the proximity of aperiphery of a stage.

FIGS. 3A and 3B are diagrams to compare the diameter of an objectiveitem mounting unit in an objective item mounting stage of a plasmaprocessing apparatus.

FIGS. 4A and 4B are diagrams showing a distribution example of depositedsubstance fixed onto a periphery of a rear surface of an objective item.

FIGS. 5A to 5C are diagrams to explain processing steps using a plasmaprocessing apparatus.

FIGS. 6A to 6C are diagrams to explain a second embodiment of thepresent invention.

FIG. 7 is a diagram to explain the second embodiment of the presentinvention.

FIGS. 8A to 8C are diagrams to explain a third embodiment of the presentinvention.

FIGS. 9A and 9B are diagrams to explain a fourth embodiment of thepresent invention.

FIG. 10 is a diagram to explain a fifth embodiment of the presentinvention.

FIG. 11 is a diagram to explain a sixth embodiment of the presentinvention.

DESCRIPTION OF THE EMBODIMENTS

Description will now be given of an embodiment by referring to thedrawings. FIG. 1 shows a first embodiment of a plasma processingapparatus of the present invention. As can be seen from FIG. 1, anantenna 3 is arranged in a processing chamber 1 to emit anelectromagnetic wave. The antenna 3 is connected via a matching unit 6to a high-frequency power source 5 to generate plasma. A shower plate 11is disposed below the antenna 3. Processing gas is delivered into theprocessing chamber 1 through gas holes formed in the shower plate 11.

To lower the pressure in the processing chamber 1 down to apredetermined pressure, there are disposed an exhaust unit 7 such as aturbo molecular pump and a butterfly valve (not shown) in a stage beforethe exhaust unit 7 to adjust the pressure in the processing chamber 1 toa predetermined pressure. In the processing chamber 1, an objective itemmounting stage 4 to mount thereon an objective item 2 is disposed. Inthe stage 4, pusher pins (not shown) are disposed to move the objectiveitem 2 upward.

FIG. 2 shows details of a region in the proximity of a periphery of thestage 4 of FIG. 1. As shown in FIGS. 1 and 2, a diameter 21 of amounting unit 41 of the stage 4 is less than a diameter 30 of theobjective item 2. Therefore, when the objective item 2 is mounted on themounting unit 41, the periphery of the objective item 2 is beyond aperiphery of the mounting unit 41. As a result, space 32 continuous toprocessing space of the processing chamber 1 is formed below theperiphery of the objective item 2.

FIGS. 3A and 3B are diagrams to compare a diameter 20 of the mountingunit in the mounting stage (FIG. 3A) of a plasma processing apparatusemployed for the etching processing with a diameter 21 of the mountingunit in the mounting stage (FIG. 3B) of a plasma processing apparatusemployed for the resist ashing.

To remove the deposited substance fixed onto the periphery of the rearsurface of the objective item during the ashing processing, it isrequired, when the item is mounted on the mounting stage (FIG. 3B) ofthe plasma processing apparatus employed for the ashing processing, thatthe deposited substance is not brought into contact with the mountingunit. Therefore, the diameter 21 of the mounting unit in the mountingstage (FIG. 3B) of the plasma processing apparatus for the resist ashingis required to be less than the diameter 20 of the mounting unit in themounting stage (FIG. 3A) of the plasma processing apparatus for theetching processing.

FIGS. 4A and 4B show a distribution example of deposited substance fixedonto a periphery of a rear surface of an objective item. In thisexample, the deposited substance is more widely distributed in theleft-hand side of the rear surface (c of FIG. 4B) than in the right-handside thereof (d of FIG. 4B).

This indicates that when the objective item is transported onto themounting stage of the plasma processing apparatus in the etchingprocessing, the objective item is mounted at a position slightlydeviated or shifted to the left side relative to the mounting stage. Theshift is due to deviation in the transport target position when theobjective item is transported by, for example, a transporting robot.

Therefore, the diameter 21 of the mounting unit of the mounting stagedisposed in the ashing processing chamber is to be determined inconsideration of also the deviation in the transport target position towhich the objective item is transported by a transporting robot. Assumethat the maximum deviation of the transport target position is α whenthe objective item is transported onto the mounting stage (FIG. 3A) ofthe plasma processing apparatus employed for the etching processing, thediameter 20 of the mounting unit in the mounting stage is a, the maximumdeviation of the transport target position is β when the objective itemis transported onto the mounting stage (FIG. 3B) of the plasmaprocessing apparatus employed for the ashing processing, and thediameter 21 of the mounting unit in the mounting stage is b. It is thendesirable to hold the relationship as below.

b≦a−(α+β)×2  (1)

If distance 22 (FIG. 2) required between the mounting unit in themounting stage and the deposited substance on the periphery of the rearsurface of the objective item is represented as γ, it is desirable tohold the relationship as below.

b≦a−(α+β+γ)×2  (2)

Assume that the maximum deviation α of the transport target position inthe etching processing is 0.5 millimeter (mm), the diameter a of themounting unit in the mounting stage disposed in the ashing processingchamber is 294 mm, the maximum deviation β of the transport targetposition in the ashing processing is 0.5 mm, and the distance γ requiredbetween the mounting unit placed on the mounting stage and the depositedsubstance on the periphery of the rear surface of the objective item isone millimeter. In this situation, it is desirable that the diameter ofthe mounting unit in the stage placed in the ashing apparatus is equalto or less than 290 mm.

It is desired that a space 32 extending below the periphery of the rearsurface of the objective item has a height 31 which allows plasmaparticles sufficiently reach deposited substance 23 fixed onto theperiphery (FIG. 2). For this purpose, the height 31 is set to a lengthequal to or more than a mean free path of the plasma particles. It isdesirable that the height 31 of the space 32 is at least ten times themean free path.

The processing gas for the resist ashing processing is, for example, agas prepared by adding several percent of hydrogen to He or Ar, oxygen,nitrogen, ammonia gas, or a mixed gas of hydrogen and nitrogen. Theprocessing gas has a pressure of, for example, about 100 pascal (Pa). Inthis case, the mean free path of the radicals generated in the gas orthe plasma through, for example, dissociation is about 0.1 mm.Therefore, the height 31 of the space 32 is desirably set to at leastabout one millimeter.

The mounting stage integrally includes a heater to heat the objectiveitem up to about 400° C. The stage may also be constructed to beconnected to a power source to electrostatically absorb the objectiveitem. In this case, a surface of the stage is coated with a filmprimarily including alumina or yttria through thermal spraying. It isalso possible to install a mechanism to fix the objective item onto thestage using, for example, electrostatic absorption. In such aconfiguration, to adjust the temperature of the objective item, a gasof, e.g., helium can be supplied into a space between the stage and therear surface of the objective item. Therefore, a groove may be arrangedin the mounting unit of the stage to flow the gas therethrough. Byassuming a case in which the ashing is conducted with a bias applied tothe stage, a power source may be connected to the stage to apply ahigh-frequency bias thereto.

FIGS. 5A to 5C show processing steps using the plasma processingapparatus of the embodiment. In this example, the plasma processingapparatus for the etching processing and the plasma processing apparatusfor the resist ashing are independent of each other. FIG. 5A shows afine pattern of a front surface of the objective item, FIG. 5B shows adistribution of deposited substance fixed onto a rear surface of theobjective item, and FIG. 5C shows the semiconductor producing apparatus.Arrows 26 indicate the flow of the objective item.

First, the objective item 2 is transported into a plasma processingapparatus 24 and an etched layer 28 is then etched using resist 27 as amask and a processing gas with a large deposition property resulting ina large amount of deposited substance. In this step, the depositedsubstance 23 is fixed onto a periphery of a rear surface of theobjective item 2. Next, the objective item 2 is transported into anotherplasma processing apparatus 25 for the ashing, and then the resist 27 isremoved through an ashing step. In the step, the deposited substance 23fixed onto the periphery of the rear surface is also removed. That is,according to the present invention, it is not required to use anyparticular processing step to remove the deposited substance. Areference numeral 29 depicts a lower layer.

FIGS. 6A to 6C and FIG. 7 are diagrams to explain a second embodiment ofthe present invention. FIGS. 6A to 6C are diagrams to explain upward anddownward movement of the objective item by pusher pins. FIG. 7 is a topview of the second embodiment (excepting the objective item).

In FIG. 6A, the objective item 2 is lifted over the stage by driving thepusher pins 8 upward. In FIG. 6B, upper ends of the pusher pins 8 and anupper end of the objective item are at the same height relative to thestage. In FIG. 6C, the pusher pins 8 are driven down to a position belowthe objective item.

The three pusher pins 8 are linked with each other to support theperiphery of the objective item 2 with an equal distance therebetween.The pusher pins 8 are moved upward or downward as a unit. When the upperends of the pusher pins 8 and an upper surface of the objective item 2are at almost the same height, the pusher pins 8 serve as stopper pinsto keep the objective item placed or held on the stage. Each pusher pin8 has an inclined side surface 34 as shown in FIG. 6C. Therefore, evenif the objective item 2 slightly moves in a lateral direction on thestage, the objective item 2 can be placed at an appropriate positionwhen the objective item 2 is mounted on the pusher pins 8 by driving thepusher pins 8 upward.

In the ashing processing, the pusher pins 8 are fully moved downwardrelative to the objective item 2 as shown in FIG. 6C. As a result, theplasma can be sufficiently radiated also onto the peripheral areas inthe neighborhood of the pusher pins 8. In this situation, since thepusher pins 8 are exposed to the plasma, it is favorable to produce thepusher pins 8 with a material such as SiC which rarely causes heavymetal contamination.

As above, according to the embodiment, there can be provided sufficientspace below and in lateral directions of the periphery of the rearsurface of the objective item for the plasma radiation. Also, the shiftfrom a predetermined target position of the objective item placed on thestage can be prevented and corrected.

FIGS. 8A to 8C are diagrams to explain a third embodiment of the presentinvention. In FIGS. 8A to 8C, a reference numeral 12 indicates a guide.The guide 12 is a mechanism to keep the objective item 2 held on thestage and is configured as a circumferentially continuous unit. Theguide 12 can be driven upward and downward. During the plasma processingsuch as the ashing, the guide 12 is driven down to a position below theobjective item 2. The guide 12 includes an objective item mountingsection 33 and an inclined stopper surface 34 as shown in FIG. 8B. Dueto the configuration, when the objective item 2 is lifted by driving theguide 12 upward and is then placed on the stage by driving the guide 12downward, the mounting position of the objective item 2 can becorrected. According to the third embodiment, the positional shift ofthe objective item can be more accurately corrected.

FIGS. 9A and 9B are diagrams to explain a fourth embodiment of thepresent invention. FIG. 9A is a side view of the mounting stage and FIG.9B is a top view of the mounting stage (excepting the objective item).In the fourth embodiment, guide pins 9 are arranged on a periphery ofthe stage to keep the objective item held on the stage.

Each guide pin 9 has a substantially cylindrical shape. A guide pinsupporter 10 to support the guide pins 9 can rotate in a circumferentialdirection. The structure advantageously prevents, during the ashingprocessing, occurrence of an event in which the deposited substance onthe periphery of the rear surface of the objective item cannot belocally removed due to hindrance of the pusher pins 8.

FIG. 10 is a diagram to explain a fifth embodiment of the presentinvention. Specifically, FIG. 10 is a top view of a plasma processingapparatus according to the fifth embodiment. As can be seen from FIG.10, the semiconductor processing apparatus includes a load-lock chamber16 to transport an objective item to be processed from the side ofatmosphere to the side of vacuum, an unload-lock chamber 17 to transportthe objective item from the vacuum side to the atmosphere side, twoetching processing chambers 14 to conduct predetermined etchingprocessing, two ashing processing chambers 15 to remove resist, and atransport chamber 13 to transport the objective item. In the transportchamber 13, a transport robot 18 is installed.

The diameter of the objective item mounting unit of the objective itemmounting stage arranged in each etching processing chamber 14 and thediameter of the objective item mounting unit of the objective itemmounting stage arranged in each ashing processing chamber 15 satisfy arelationship represented by expression (1) described in conjunction withthe first embodiment. In the fifth embodiment, a measuring unit 19 isdisposed in the transport chamber 13 to measure a distribution ofdeposited substance fixed onto the periphery of the rear surface of theobjective item.

After the etching processing is conducted for the objective item, themeasuring unit 19 measures the distribution of deposited substance fixedonto the periphery of the rear surface of the objective item.Thereafter, the objective item is transported into the ashing processingchamber 15. In the operation, the transport target position is adjustedby aligning a central point of the mounting stage with a central pointof an area on which the deposited substance has not been fixed tothereby mount the objective item on the mounting stage. This guaranteesthat the deposited substance fixed onto the periphery of the rearsurface of the objective item is removed through the resist ashingprocessing.

FIG. 11 is a diagram to explain a sixth embodiment of the presentinvention. The sixth embodiment employs a remote plasma processingapparatus in which a plasma generator unit 35 is disposed apart from theprocessing chamber 1 and plasma particles generated by the plasmagenerator unit 35 are delivered into the processing chamber 1. In theplasma processing apparatus, the objective item mounting stageconfigured as described in conjunction with the first embodiment can beemployed as a stage to mount thereon the objective item. Also, themounting stage configured as described for the two to fourth embodimentscan be employed as the mounting stage of the sixth embodiment.

According to the embodiments of the present invention described above,the diameter of the mounting unit in the mounting stage of the ashingprocessing apparatus is less than that of the mounting unit in themounting stage of the etching processing apparatus. As a result, thedeposited substance fixed onto the periphery of the rear surface of theobjective item can be assuredly removed through the resist ashingprocessing.

It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1-7. (canceled)
 8. A plasma processing method for use with a plasma processing apparatus comprising an etching processing apparatus including an etching mounting stage for mounting and for holding in a vacuum processing chamber an objective item to be processed, the etching mounting stage having a diameter less than a diameter of the objective item, and a plasma generating unit for generating plasma in the vacuum processing chamber and an ashing processing apparatus including an ashing mounting stage for mounting and for holding the objective item in the vacuum processing chamber, the ashing mounting stage having a diameter less than that of the etching mounting stage and a plasma generating unit for generating plasma in the vacuum processing chamber, the method comprising the steps of: mounting the objective item on the etching mounting stage and conducting etching processing for the objective item; transporting from the etching stage the objective item for which the etching processing is finished and mounting the objective item on the ashing mounting stage; and removing, during resist ashing processing by the ashing processing apparatus, deposited substance fixed onto a periphery of a rear surface of the objective item during the etching processing by the etching processing apparatus. 